Nickan Research Institute Journal of Parathyroid Disease 2345-6558 13 1 2025 01 01 Association of serum vitamin D levels with diabetes mellitus and obesity; a prospective case-control study e13296 e13296 10.34172/jpd.2025.13296 EN Farah Kadhim Alwan https://orcid.org/0009-0009-1763-4492 Ahmed Aboud Khalifa https://orcid.org/0000-0003-2094-540X Journal Article 10.34172/jpd.2025.13296 2025 07 01 2025 08 17 Introduction: Vitamin D deficiency has been implicated as a potential risk factor for metabolic disorders, including diabetes mellitus and obesity. Understanding the association between serum vitamin D levels and these conditions could guide future preventive strategies. Objectives: This study aims to investigate the relationship between serum vitamin D concentrations and the presence of diabetes mellitus and obesity through a prospective case-control design. Patients and Methods: This prospective case-control study was conducted over three months in Misan province, Iraq, involving 60 women aged 30–40 years, divided equally into healthy controls, obese, and type 2 diabetic groups. Blood samples were collected on the 10th day of the menstrual cycle and analyzed for serum 25-hydroxyvitamin D using an automated immunoassay. The study aimed primarily to compare vitamin D levels across the groups and secondarily to explore the relationship between vitamin D status and the presence of obesity and diabetes. Results: The comparative analysis of serum vitamin D levels among healthy individuals, obese individuals, and diabetes patients revealed a highly significant overall difference, with both the obese individuals and diabetic patients exhibiting notably lower vitamin D concentrations than healthy individuals. However, no significant difference was found between the vitamin D levels of obese and diabetic individuals, indicating comparable deficiencies in these metabolic disorder populations. Conclusion: The study identified a significant negative association between vitamin D concentration and both obesity and diabetes, highlighting the importance of targeted screening for metabolic disorders and vitamin D deficiency.